Plural electrically short concatenated coaxial stub antennas useful with aircraft



Sept. 29, 19 4 P. B. LEVY ETAL 3,151,327

PLURAL ELECTRICALLY SHORT CONCATENATED COAXIAL STUB ANTENNAS USEFUL WITH AIRCRAFT Filed Jan. 4, 1965 2 Sheets-Sheet l Sept. 29, 1964 P. B. LEVY ETAL 3,151,327

PLURAL. ELECTRICALLY SHORT CONCATENATED COAXIAL.

STUB ANTENNAS USEFUL WITH AIRCRAFT 2 Sheets-Sheet 2 Filed Jan. 4, 1965 United States Patent 3,151,327 PLURAL ELEQTRECALLY SHGRT C(BNCATE- NATED QOAXIAL SIUB ANTENNAS USE- FIJI. WiTl-I AIRUWT Pierre Bourirhard Levy, Maisons-Laftitte, and Jean Adr en Enron, Montrouge, France, assignors to Sud-Aviation Societe Nationaie de Constructions Aeronautiques, Paris, France Filed Jan. 4, 1963, Ser. No. 249,459 (Ilaims priority, application France, Jan. 16, 1962, 884,941, Patent 1,319,941

l0 Qlaims. (Cl. 343705) It is well known to utilize whip antennae consisting of a hollow conductive cylinder of more or less regular sec tion, the length of which is less than that of the corresponding single-wire antenna of identical wavelength. When the height of the cylinder reaches approximately one-quarter of the transmission or reception wavelength, the whip antenna is said to be a or quarter-wave antenna.

Such antennae oifer undeniable advantages such as simplicity of construction, a wide pass-band and circular coverage.

. However, such antennae have a very considerable geometrical height, which can entail serious drawbacks in many applications.

With a view to reducing the geometrical height of such antennae while at the same time retaining as many of their advantages as possible, this invention has for its object to provide a hollow-stub radio antenna divided into a multiplicity of hollow stubs with a radiating cylinder and an axial internal line except for the hollow stub which is the farthest from the antenna input and which only consists of a radiatin cylinder, the sum of the heights of said stubs being substantially equal to the height of the equivalent quarter-wave whip antenna. The cylindrical stubs are preferably disposed side by side and insulated from earth. They are so interconnected that, jointly, they radiate in similar fashion to a single quarterwave whip antenna.

It will already be noted at this stage that the considerable shortening achieved in this way permits a simplified construction for certain applications, if only with respect to the means utilized for strengthening the installation of the antenna. This advantage is of particular importance in the case of antennae used on high-speed aircraft, when the single-Wire type becomes difficult to mount securely enough for it to withstand the drag inovlved.

In accordance with the present invention, for such aeronautical applications, the multiple stubs are preferably arrayed in a same plane parallel with the fore-and-aft axis of the aircraft. In addition, it will be of advantage to fair the system for reduced drag, such fairing preferably being made of aplastic in conjunction with a filler material of very low density which reinforces and rigidly binds the component parts of the antenna to one another.

The scope of the invention additionally covers all industrial applications of the antenna hereinbefore disclosed, notably in the aeronautical field and more particularly on high speed aircraft, missiles or other aeronautical vehicles.

The description which follows with reference to the accompanying drawings, which are filed by way of example only and not of limitation, will give a clear under standing of how the invention can be carried into practice and will disclose yet further particularities thereof.

In the drawings:

FIGURE 1 is a schematic illustration of a conventional whip antenna;

3,l5i,327 Patented Sept. 29, 1964 FIGURE 2 is a schematic illustration of a preferred embodiment of a multiple-stud radio antenna executed according to this invention;

FIGURE 3 illustrates a method of adjusting the currents in the first stub of the antenna of FIGURE 2;

FIGURE 4 is a schematic illustration of a second em bodiment of a multiple-stub antenna according to this invention;

FIG. 5 is an exploded view of a multiple-stub radio antenna adapted for mounting on an aircraft for piloting the same during instrument landings;

FIG. 6 is a longitudinal section of the antenna of FIG. 5, as mounted, along its longitudinal plane of symmetry;

FIG. 7 is a sectional view taken through the line VII-- VII of FIG. 6, the filler material being assumed to have been removed;

FIG. 8 is an enlargement of a detail of the antenna of FIGS. 5 through 7; and

FIG. 9 is a schematic illustration of another embodiment of a multiple-stub antenna according to this invention.

Referring first to FIG. 1, numeral 1 denotes a cylinder the length of which is substantially equal to numeral 2 a metal reference plate symbolizing the ground, and numeral 3 the coaxial feed cable. This figure schematically represents a conventional quarter-wave whip antenna.

In FIG. 2, I, II, N designate the n stubs of the multi-stub antenna according to the invention which comprise radiating cylinders CI, CII, CN and, except for cylinder CI'which is the farthest from the antenna input, coaxial inner lines AII, AN respectively connected to the preceding cylinders CI, C(N1) by means of conductors 41, ill, 4(N1). The successive stubs can be of difierent shape and height, but the sum of their heights is equivalent to the height of the quarter-wave whip antenna for which they are substituted. L L L are matching induction coils or reactances as hereinafter described, said reactances being respectively parallel-connected with a common metal plate 2 and with conductors 41, 4(N-1) and conductor 4N connected in turn with the antenna coaxial feed cable 3.

For such a system to radiate in identical fashion to the quarter-wave whip antenna of FIG. 1, the various coils L L L are adjusted as follows:

The impedance of the equivalent quarter-wave whip antenna shown in FIG. 1 is first measured at the frequency and its adjustment elements be the same asthat of the quarter-wave whip antenna of FIG. 1, as measured at the frequency The length of the conductor 4 is then used for the coupling conductor 4I between stubs I and II.

The same procedure is adopted for the system comprising stubs I and H, induction coil L being adjusted so that the impedance phase of the system consisting of stubs I, II and their adjustmentelements is the same as that of the quarter-wave whip antenna of FIGpl, as measured at the frequency and so on.

Experience shows that if the various stubs I, II N are disposed side by side and narrowly spaced from one another .in relation to the wavelength, a multiple-stub antenna of FIG. 1 according to the present invention will have a radiation pattern equivalent to that of the quarter-wave whip antenna, however, with a pass-band which, though narrower, is nonetheless adequate for a great many applications.

By way of example, the applicants have found that with a three-stub antenna of total height substantially equal to it w as possible to achieve a me. pass-band with a standing wave ratio of less than 5 on 332 me, whereas the corresponding quarter-Wave whip antenna has a 40 mc. pass-band with a standing wave ratio of less than 5 on this same frequency of 332 mc.

An alternative embodiment of a multiple-stub antenna according to this invention is shown in FIG. 4, wherein the parallel-connected induction coils L L L of FIG. 2 have been replaced by capacitors C C C respectively series-connected with conductors 4-1,

In the particular form of construction illustrated in FIGS. 5 through 8, the multiple hollow-stub antenna is adapted for mounting on an aircraft to permit piloting thereof during instrument landings, the frequency utilized being of the order of 300 me. .This antenna comprises a bonded mounting-plate 11 usable for the fixation of the antenna on the aircraft structure and supporting two connectors 12 and 12a which, in the illustrated example, are

connected to two receivers.

On the mounting-plate 11 are mounted threeelements 13, each consisting of an outer metal tube 14 closed at its top by a metal mass 15 which connects it to a coaxial rod 16 the base of which is inserted into a metal sheath 17 which is in turn embedded in an insulating filler material 18 and screwed as at 19 into plate 11. Two metal rods 20 and 20a retain the insulating mass 18 securely inside the tube. The lengths of said metal tubes 14 are such that their sum be equal to the length of the corresponding quarter-wave whip antenna.

A connection rod 28 is tin-soldered to the connectors 12, 12a and to the tube 14 of element 13 which is the closest to said connectors. Metal rods 29 screwed into the base of the coaxial rods 16 of the two elements 13 closest to said connectors are tin-soldered to the tubes 14 of the two elements 13 farthest from said connectors, respectively. Therefore, the tubes 14 of the three elements 13 act as three'radiating elements.

The system is coupled to three parallel-connected matching reactances. The first reactance 21 connected into the input circuit consists of a simple loop which is tin-soldered to the plate 11 and to the connection rod 28. The two others 22 are adjustable. Each one of said other reactances consists of a hollow cylindrical body 23 made of insulating material and connected to plate 11 by screwing of its base to a metal support 27 screwed to said plate and the lower surface of which is flush with the lower face of said plate. About said hollow body 23 is wound the conductive element 24 which interconnects thetube 14 of the corresponding radiating element and said support 27. Within this hollow body is disposed a metal piston 25 havig a threaded stem 26,

whereby it is slidable by the co-operation of stem 26 with the base 27 securing said hollow body. Said piston is shifted until the associated reactance has been matched, after which the stem 26 is levelled off flush with the lower face of plate 11.

With the object of reducing drag, the thus formed antenna is placed beneath an insulating fairing 34) made for instance of resin-coated fiberglass, which fairing furthermore serves to protect the system as a whole. A synthetic foam filler material 31, preferably consisting of polyurethane foarn, rigidly secures the elements contained Within the fairing, whereby to ensure very good resistance to shock loadings and vibration.

The insulating material used for the filler 18 and the hollow bodies 23 consists of a synthetic resin of the polytetrafiuorethylene class, such as that known by the trademark Tefion. The mechanical components can be made with advantage of copper or silvered brass.

It will of course be understood that the aerodynamic shape of the fairing 3% must be adapted to the speed range of the aircraft and be designed to offer minimum drag. In the specific case of the antenna illustrated, the antenna is so positioned on the aircraft as to provide optimum coverage, namely in the front part of the aircraft, for example in the nose of thefuselage. In this particular application, to wit flight control during instrument landings, transmission is polarized horizontally and the antenna is so disposed that its longitudinal symmetry plane be horizontal; it would be disposed in a vertical plane were transmission to be polarized vertically.

It will be manifest that several modifications can be made to the specific embodiments h'ereinbefore described, without departing from the scope of the invention as defined in the appended claims. By way of example, in the case of the antenna of FIGS. 5 through 8, the reactances, as explained precedingly, could be replaced by series-connected capacitors. Similarly, any desired combination of the adjustment circuits could be utilized, an example being parallel-connected reactances in circuit with seriesconnected capacitors as illustrated in FIG. 9 wherein the same reference numerals are respectively applied to elements similar'to those of FIGS. 2 and 4. Lastly, the invention is likewise applicable to antennae the radiation height of which differs from and even to voice communications antennae.

What we claim is:

1. A radio quarter-wave antenna comprising, in combination, a multiplicity of hollow stubs disposed side by side and not earthed, the sum of the heights of said stubs being substantially equal to the-height of the equivalent quarter-wave whip antenna, the stub which is the farthest from the antenna input consisting of a radiating cylinder while each one of the other stubs consists of a radiating cylinder and of a coaxial internal line; conductors respectively connecting each radiating cylinder to the coaxial terminal line of the following hollow stub toward the antenna input, a coaxial feed cable, an input connector interconnecting said cable and the radiating cylinder of the hollow'stub closest to said cable, and means for adjusting the radiation of each hollow stub so that said hollow stubs jointly radiate as said quarter-wave whip antenna.

2. A radio quarter-wave antenna according to claim 1, wherein the means for adjusting the radiation of each hollow stub comprises an adjustable reactance parallelmounted between its radiating cylinder and earth.

3. A radio quarter-wave antenna according to claim 1, wherein the means for adjusting the radiation of each hollow stub comprises an adjustable capacitor inserted intothe conductor connected to its radiating cylinder.

4. A radio quarter-wave antenna according to claim 1, wherein the means for adjusting the radiation of each 5 hollow stub comprises an adjustable reactance parallelmounted between its radiating cylinder and earth, and an adjustable capacitor inserted into the conductor connected to said radiating cylinder.

5. A radio quarter-Wave antenna, for use in the aeronautical field and more specifically on high-speed aerodynes, aircraft, missiles and like vehicles, comprising, in combination, a multiplicity of hollow stubs disposed side by side with their axes located in a common plane parallel with the fore-and-aft axis of the aircraft, the sum of the heights of said stubs being substantially equal to the height of the equivalent quarter-wave whip antenna, the stub which is the farthest from the antenna input consisting of a radiating cylinder while each one of the other stubs consists of a radiating cylinder and of a coaxial internal line; conductors respectively connecting each radiating cylinder to the coaxial internal line of the following hollow stub toward the antenna input, a coaxial feed cable, an input conductor interconnecting said cable and the radiating cylinder of the hollow stub closest to said cable, and means for adjusting the radiation of each hollow stub so that said stubs jointly radiate as said hollow quarter-wave Whip antenna.

6. A radio quarter-wave antenna, for use in the aeronautical field and more specifically on high-speed aerodynes, aircraft, missiles and like vehicles, comprising, in combination, a multiplicity of hollow stubs disposed side by side with their axes located in a common plane parallel with the fore-and-aft axis of the aircraft, the sum of the heights of said stubs being substantially equal to the height of the equivalent quarter-Wave whip antenna, each hollow stub comprising an external metal tube, a metallic rod disposed within said tube coaxially there- With, a metallic mass interconnecting the tops of said tube and rod, a metal sheath through which the base of said rod is inserted, an insulating mass filling the base of said tube and into which said sheath is embedded, and means for interconnecting said tube and said insulating mass; an earthed metal base-plate secured on the aircraft structure, screws respectively connecting said base-plate and said insulating masses, conductors connecting each tube, except the closest to the antenna input, to the coaxial internal rod of the preceding hollow stub, at least one connector carried by said base-plate and adapted to be connected to a receiver, an input conductor intercon- 6 necting each connector and the tube of the hollow stub closest to the antenna input, means for adjusting the radiation of said hollow stubs, and means for reducing the drag of the antenna.

7. An antenna, according to claim 6, wherein the means for adjusting the radiation of the hollow stubs comprises, for the hollow stub closest to the antenna input, a conductive loop interconnecting the base-plate and the input conductor, and, for each other hollow stub, a hollow cylindrical body of insulating material, a metal support screwed to said base-plate and into the base of said hollow cylindrical body, having a central tapping and the lower face of which is fiush'with that of said base-plate, a conductive element Wound about said hollow cylindrical body and interconnecting said support and the tube of said hollow stub, a metal piston displaceable within said hollow cylindrical body, and a threaded stem integral with said piston and engaging said tapping, said stem being levelled off with the lower face of said baseplate as soon as said piston has been shifted until the reactance formed by it and said conductive element has been matched.

8. An antenna, according to claim 7, wherein the insulating material forming the insulating masses filling the base of the tubes and the hollow cylindrical bodies consists of a synthetic resin of the polytetrafluorethylene class.

9. An antenna according to claim 6, wherein the means for reducing the antenna drag comprises an insulating fairing of aerodynamic shape, secured on the base-plate and housing the component parts of the antenna, and a filler material of very low density disposed within said fairing for reinforcing the latter and preventing any relative movement of said component parts.

10. An antenna according to claim 9, wherein the filler material consists of a synthetic foam.

References Cited in the tile of this patent UNITED STATES PATENTS 2,425,887 Lindenblad Aug. 19, 1947 2,531,476 Schriefer Nov. 28, 1950 2,615,131 Lindenblad Oct. 21, 1952 2,858,534 Shanklin Oct. 28, 1958 

1. A RADIO QUARTER-WAVE ANTENNA COMPRISING, IN COMBINATION, A MULTIPLICITY OF HOLLOW STUBS DISPOSED SIDE BY SIDE AND NOT EARTHED, THE SUM OF THE HEIGHTS OF SAID STUBS BEING SUBSTANTIALLY EQUAL TO THE HEIGHT OF THE EQUIVALENT QUARTER-WAVE WHIP ANTENNA, THE STUB WHICH IS THE FARTHEST FROM THE ANTENNA INPUT CONSISTING OF A RADIATING CYLINDER WHILE EACH ONE OF THE OTHER STUBS CONSISTS OF A RADIATING CYLINDER AND OF A COAXIAL INTERNAL LINE; CONDUCTORS RESPECTIVELY CONNECTING EACH RADIATING CYLINDER TO THE COAXIAL 